Rough Idle Causes? Options

[Nano]

What could cause the car to idle roughly when not moving but in gear? When its still but in gear ( Ie: Redlight ), it vibrates rather roughly, when its in park its fine, and when its moving its fine. It also on occasion has sharp drops in rpms ( around the 300 mark ) over and over again, typically when running the AC. Anyone have any idea what could be causing this?

This post has been edited by Nano: Apr 19, 2006 - 2:18 PM

[95CelicaST]

Do you have an Auto? Manual? Have you unhooked the battery recently?

I ask because when you unhook the battery the ECU resets. When you hook it back up you need to let it sit and go through the re-learn process, or it will drive like crap. I did this a while back and went through a tank of gas in a day. not fun.

[Nano]

[quote name='95CelicaST' date='Apr 19, 2006 - 2:39 PM' post='423580']
Do you have an Auto? Manual? Have you unhooked the battery recently?[/quote]

Auto, yes... sorta anyway. I bought it two weeks ago, it had a non spec battery on it, and it ran like that then. As of yesterday, i replaced the non spec battery, since the other died. :\

[qoute]
I ask because when you unhook the battery the ECU resets. When you hook it back up you need to let it sit and go through the re-learn process, or it will drive like crap. I did this a while back and went through a tank of gas in a day. not fun.
[/quote]

How do you do that, exactly?

[95CelicaST]

How do you do that, exactly?

Unhook the battery, let it sit for a bit, and then hook it back up. Once you have done that turn the car on and just let it run. If you have an Automatic and a copy of the Toyota Manual you will be able to find the information in there.

COMPUTER RELEARN PROCEDURES
1994 Toyota Celica
GENERAL INFORMATION
Computer Relearn Procedures
All Models
* PLEASE READ THIS FIRST *
The following general procedures are to be used if
driveability problems are encountered after power loss or battery has
been disconnected. These procedures may provide an aid in eliminating
these problems.
To reduce the possibility of complaints, after any service
which requires battery power to be disconnected, vehicle should be
road tested.
COMPUTER RELEARN PROCEDURES
Vehicles equipped with engine or transmission computers may
require a relearn procedure after vehicle battery is disconnected.
Many vehicle computers memorize and store vehicle operation patterns
for optimum driveability and performance. When vehicle battery is
disconnected, this memory is lost. The computer will use default data
until new data from each key start is stored. As computer memorizes
vehicle operation for each new key start, driveability is restored.
Vehicle computers may memorize vehicles operation patterns for 40 of
more key starts.
Customers often complain of driveability problems during
relearn stage because vehicle acts differently then before being
serviced. Depending on type and make of vehicle and how it is
equipped, the following complaints (driveability problems) may exist:
* Harsh Or Poor Shift Quality
* Rough Or Unstable Idle
* Hesitation Or Stumble
* Rich Or Lean Running
* Poor Fuel Mileage
These symptoms and complaints should disappear after a number
of drive cycles have been memorized. To reduce the possibility of
complaints, after any service which requires battery power to be
disconnected, vehicle should be road tested. If a specific relearn
procedure is not available, the following procedure may be used:
Automatic Transmission
* Set parking brake, start engine in "P" or "N" position.
Warm-up vehicle to normal operating temperature or until
cooling fan cycles.
* Allow vehicle to idle for one minute in "N" position. Select
"D" and allow engine to idle for one minute.
* Accelerate at normal throttle position (20-50%) until vehicle
shifts into top gear.
* Cruise at light to medium throttle.
* Decelerate to a stop, allowing vehicle to downshift, and use
brakes normally.
* Process may be repeated as necessary.
Manual Transmission
* Place transmission in Neutral position.
* Ensure emergency brake has been set and all accessories
are turned off.
* Start engine and bring to normal operating temperature.
* Allow vehicle to idle in Neutral for one minute.
* Initial relearn is complete: process will be completed during
normal driving.
Some manufacturers identify a specific relearn procedure
which will help establish suitable driveability during relearn stage.
These procedures are especially important if vehicle is equipped with
and electronically controlled automatic transmission or transaxle.
Always complete procedure before returning vehicle to customer.

This post has been edited by 95CelicaST: Apr 19, 2006 - 2:55 PM

[Nano]

How do you do that, exactly?

Unhook the battery, let it sit for a bit, and then hook it back up. Once you have done that turn the car on and just let it run. If you have an Automatic and a copy of the Toyota Manual you will be able to find the information in there.

COMPUTER RELEARN PROCEDURES
1994 Toyota Celica
GENERAL INFORMATION
Computer Relearn Procedures
All Models
* PLEASE READ THIS FIRST *
The following general procedures are to be used if
driveability problems are encountered after power loss or battery has
been disconnected. These procedures may provide an aid in eliminating
these problems.
To reduce the possibility of complaints, after any service
which requires battery power to be disconnected, vehicle should be
road tested.
COMPUTER RELEARN PROCEDURES
Vehicles equipped with engine or transmission computers may
require a relearn procedure after vehicle battery is disconnected.
Many vehicle computers memorize and store vehicle operation patterns
for optimum driveability and performance. When vehicle battery is
disconnected, this memory is lost. The computer will use default data
until new data from each key start is stored. As computer memorizes
vehicle operation for each new key start, driveability is restored.
Vehicle computers may memorize vehicles operation patterns for 40 of
more key starts.
Customers often complain of driveability problems during
relearn stage because vehicle acts differently then before being
serviced. Depending on type and make of vehicle and how it is
equipped, the following complaints (driveability problems) may exist:
* Harsh Or Poor Shift Quality
* Rough Or Unstable Idle
* Hesitation Or Stumble
* Rich Or Lean Running
* Poor Fuel Mileage
These symptoms and complaints should disappear after a number
of drive cycles have been memorized. To reduce the possibility of
complaints, after any service which requires battery power to be
disconnected, vehicle should be road tested. If a specific relearn
procedure is not available, the following procedure may be used:
Automatic Transmission
* Set parking brake, start engine in "P" or "N" position.
Warm-up vehicle to normal operating temperature or until
cooling fan cycles.
* Allow vehicle to idle for one minute in "N" position. Select
"D" and allow engine to idle for one minute.
* Accelerate at normal throttle position (20-50%) until vehicle
shifts into top gear.
* Cruise at light to medium throttle.
* Decelerate to a stop, allowing vehicle to downshift, and use
brakes normally.
* Process may be repeated as necessary.
Manual Transmission
* Place transmission in Neutral position.
* Ensure emergency brake has been set and all accessories
are turned off.
* Start engine and bring to normal operating temperature.
* Allow vehicle to idle in Neutral for one minute.
* Initial relearn is complete: process will be completed during
normal driving.
Some manufacturers identify a specific relearn procedure
which will help establish suitable driveability during relearn stage.
These procedures are especially important if vehicle is equipped with
and electronically controlled automatic transmission or transaxle.
Always complete procedure before returning vehicle to customer.

Hmm. Well, i've been driving it, so i suppose normal driving wouldnt be suitable in this case. I'll try that out, and see how it works, because i have many of those symptoms.

[Nano]

This seems to have cleared it up, But i'll post again after tomorrows lunch ( Since thats when it usually acts up, full AC, lots of heat, etc ) and mention whether or not that sorted it.

[CheesyLobster]

i'd be surprised if that fixes it...

[Nano]

i'd be surprised if that fixes it...

...

Then make a suggestion as to what you think it could be, perhaps?

[axelrduvirage]

NFW....i was looking for a resonable explaination for all my idling troubles, looks like i found it!



i suspect my battery is crap 'caus every once in a while everything resets-- clock, radio, Sirius receiver and lo and behold the car runs rough, stalls before i can get it into gear, . after a few kms everything is back to normal. the car learns, yeah?